Autonomic dysfunction following mild traumatic brain injury

Quantitative Pupillometry Predicts Return to Play and Tracks the Clinical Evolution of Mild Traumatic Brain Injury in US Military Academy Cadets: A Military Traumatic Brain Injury Initiative Study

BACKGROUND AND OBJECTIVES

The objective of this study was to determine the utility of the pupillary light reflex use as a biomarker of mild traumatic brain injury (mTBI).

METHODS

This prospective cohort study was conducted at The US Military Academy at West Point. Cadets underwent a standard battery of tests including Balance Error Scoring System, Sports Concussion Assessment Tool Fifth Edition Symptom Survey, Standard Assessment of Concussion, and measure of pupillary responses. Cadets who sustained an mTBI during training events or sports were evaluated with the same battery of tests and pupillometry within 48 hours of the injury (T1), at the initiation of a graded return to activity protocol (T2), and at unrestricted return to activity (T3).

RESULTS

Pupillary light reflex metrics were obtained in 1300 cadets at baseline. During the study period, 68 cadets sustained mTBIs. At T1 (<48 hours), cadets manifested significant postconcussion symptoms (Sports Concussion Assessment Tool Fifth Edition P < .001), and they had decreased cognitive performance (Standardized Assessment of Concussion P < .001) and higher balance error scores (Balance Error Scoring System P < .001) in comparison with their baseline assessment (T0). The clinical parameters showed normalization at time points T2 and T3. The pupillary responses demonstrated a pattern of significant change that returned to normal for several measures, including the difference between the constricted and initial pupillary diameter (T1 P < .001, T2 P < .05), dilation velocity (T1 P < .01, T2 P < .001), and percent of pupillary constriction (T1 P < .05). In addition, a combination of dilation velocity and maximum constriction velocity demonstrates moderate prediction ability regarding who can return to duty before or after 21 days (area under the curve = 0.71, 95% CI [0.56-0.86]).

CONCLUSION

This study's findings indicate that quantitative pupillometry has the potential to assist with injury identification and prediction of symptom severity and duration.

Psychological Constructs From the Fear Avoidance Model and Beyond as Predictors for Persisting Symptoms After Concussion: An Integrative Review

OBJECTIVES

To identify the range of evidence for relationships between psychological factors using the Fear Avoidance Model (FAM) as a guiding framework and relevant clinical outcomes in adult patients with persisting symptoms after concussion (PSaC), develop a comprehensive understanding of psychological factors that have been identified as predictors of clinical outcomes for PSaC, and contribute to the theoretical framework of the FAM for PSaC.

DATA SOURCES

Six databases (CINAHL, Embase, PsycINFO, PubMed, SportDiscus, and Web of Science) were searched by a librarian for empirical and theoretical publications and experimental and quasi-experimental study designs. The literature search was not limited by publication date restrictions. Gray literature, with the exception of doctoral dissertations, was excluded.

STUDY SELECTION

We included studies in the English language consisting of human participants aged ≥18 years. Articles must have included both outcomes pertaining to PSaC (≥3mo after injury) and psychological constructs.

DATA EXTRACTION

One reviewer extracted data from the resulting studies using a standardized data extraction form designed for this review. Two reviewers independently assessed risk of bias using the Quality in Prognosis Studies tool.

DATA SYNTHESIS

This review found numerous psychological constructs, some directly linked to the FAM, that have potential prognostic relationships with PSaC. However, research remains limited and some psychological factors central to FAM were only identified in a small number of studies (catastrophizing, cogniphobia, and avoidance), whereas other psychological factors were studied more extensively (anxiety and depression).

CONCLUSIONS

There is the need for additional evidence, and this integrative review provides an adaptation of the FAM for PSaC to be used as a guiding preliminary framework for future research. Future research should aim to include psychological factors proposed in this modified FAM to fully understand PSaC.

Measurement of improvement on repeat exercise intolerance testing for suspected dysautonomia in protracted concussion recovery: a retrospective cohort study

BACKGROUND

Research has demonstrated concussion likely causes autonomic dysfunction leading to exercise intolerance.

OBJECTIVE

To measure improvement in exercise intolerance due to suspected dysautonomia associated with protracted concussion recovery, using objective measurements on a Buffalo Concussion Treadmill Test (BCTT) following participation in a prescribed exercise program.

METHODS

This is a retrospective cohort study of 101 patient charts post-concussion. Exercise intolerance was assessed using a BCTT to identify suspected dysautonomia and an exercise prescription was provided using guidelines for treating concussion-associated exercise intolerance. Patients without symptom improvement and/or inability to achieve 80-85% of age-expected maximum heart rate (HR) without symptom exacerbation received a repeat BCTT.

RESULTS

Twelve patient charts met inclusion criteria and were included in data analysis. There were significant improvements from pre-intervention to post-intervention testing in: maximum BCTT stage mean scores (p = .02); maximum HR mean scores (p = .01); prescription HR (RxHR) mean scores (p = .01); and HR delta (HR δ ) mean scores (p = .00).

CONCLUSIONS

Maximum stage, HR threshold, RxHR, and newly identified HR delta (HR δ ) are potential objective measurements of progress for dysautonomia treatment post-concussion. Future studies are indicated to create a tailored protocol in the management of protracted concussion-associated dysautonomia.

Heart Rate Variability in Concussed College Athletes: Follow-Up Study and Biological Sex Differences

Finding reliable biomarkers to assess concussions could play a pivotal role in diagnosis, monitoring, and predicting associated risks. The present study aimed to explore the use of heart rate variability (HRV) in the follow-up of concussions among college athletes and to investigate the relationships between biological sex, symptomatology, and HRV values at baseline and after a concussion. Correlations between measures were also analyzed. A total of 169 (55 females) athletes aged 16 to 22 years old completed baseline testing, and 30 (8 females) concussion cases were followed. Baseline assessment (T1) included psychosocial and psychological questionnaires, symptoms report, and four minutes of HRV recording. In the event of a concussion, athletes underwent re-testing within 72 h (T2) and before returning to play (T3). Baseline findings revealed that girls had higher %VLF while sitting than boys, and a small negligible correlation was identified between %HF and total symptoms score as well as %HF and affective sx. Post-concussion analyses demonstrated a significant effect of time × position × biological sex for %HF, where girls exhibited higher %HF at T3. These findings suggest disruptions in HRV following a concussion and underscore biological sex as an important factor in the analysis of HRV variation in concussion recovery trajectory.

Wearable Sensors Detect Movement Differences in the Portable Warrior Test of Tactical Agility After mTBI in Service Members

INTRODUCTION

Assessment of functional recovery of service members following a concussion is central to their return to duty. Practical military-relevant performance-based tests are needed for identifying those who might need specialized rehabilitation, for evaluating the progress of recovery, and for making return-to-duty determinations. One such recently developed test is the 'Portable Warrior Test of Tactical Agility' (POWAR-TOTAL) assessment designed for use following concussion in an active duty population. This agility task involves maneuvers used in military training, such as rapid stand-to-prone and prone-to-stand transitions, combat rolls, and forward and backward running. The effect of concussion on the performance of such maneuvers has not been established.

MATERIALS AND METHODS

The Institutional Review Board-approved study was conducted at Ft. Bragg, North Carolina, on 57 healthy control (HC) service members (SMs) and 42 well-matched SMs who were diagnosed with concussion and were referred for physical therapy with the intent to return to duty. Each study participant performed five consecutive trials of the POWAR-TOTAL task at full exertion while wearing inertial sensors, which were used to identify the constituent task maneuvers, or phases, and measure their durations. Statistical analyses were performed on durations of three main phases: (1) rising from prone and running, (2) lowering from vertical to prone, and (3) combat rolls.

RESULTS

None of the three phases showed significant correlation with age (range 18-45 years) in either group. Gradual improvement in all three phase durations across five trials was observed in the HC group, but not in the concussed group. On average, control subjects performed significantly faster (P < .004 or less) than concussed subjects in all trials in the lowering and rolling phases, but less so in the rising/running phase. Membership in the concussed group had a strong effect on the lowering phase (Cohen's d = 1.05), medium effect on the rolling phase (d = 0.72), and small effect on the rising/running phase (d = 0.49). Individuals in the HC group who had a history of prior concussions were intermediate between the concussed group and the never-concussed group in the lowering and rolling phases. Duration of transitional movements (lowering from standing to prone and combat rolls) was better at differentiating individuals' performance by group (receiver operating characteristic area under the curve [AUC] = 0.83) than the duration of the entire POWAR-TOTAL task (AUC = 0.71).

CONCLUSIONS

Inertial sensor analysis reveals that rapid transitional movements (such as lowering from vertical to prone position and combat rolls) are particularly discriminative between SMs recovering from concussion and their concussion-free peers. This analysis supports the validity of POWAR-TOTAL as a useful tool for therapists who serve military SMs.

Pediatric Sports-Related Concussion: An Approach to Care

Sports-related concussion (SRC) is a common sports injury in children and adolescents. With the vast amount of youth sports participation, an increase in awareness of concussion and evidence that the injury can lead to consequences for school, sports and overall quality of life, it has become increasingly important to properly diagnose and manage concussion. SRC in the student athlete is a unique and complex injury, and it is important to highlight the differences in the management of child and adolescent concussion compared with adults. This review focuses on the importance of developing a multimodal systematic approach to diagnosing and managing pediatric sports-related concussion, from the sidelines through recovery.

Association between perceived distress and salivary cortisol in veterans with mTBI

Mild traumatic brain injury (mTBI) is one of the most common injuries experienced by Veterans and can frequently result in a variety of post-concussive symptoms. Post-concussive headaches (PCH), one of the most common symptoms, can persist for years after the injury occurred. The long-lasting impacts of PCH can be extremely distressing for Veterans, thus necessitating the need to find reliable biomarkers that directly relate to subjective feelings of distress. Yoga-based interventions have been shown to improve both subjective and objective markers of stress. Techniques used in yoga, such as the focus on releasing muscular tension, are also recommended as strategies for treating PCH. Thus, yoga-based interventions provide a unique context for the comparison of subjective and objective measures of distress in Veterans with PCH. In this secondary, exploratory analysis, we examined the relationship between perceived distress and cortisol in sixteen Veterans with mTBI and long-term PCH within the context of a yoga intervention feasibility study. The Visual Analogue Scale (VAS), a validated tool for measuring subjective distress, was administered to participants immediately before and after 75-min yoga classes, which occurred twice weekly over eight weeks. Participants also provided salivary cortisol (pre- and post-yoga) at in-person sessions (eight) to compare to changes in VAS scores. We found that VAS scores were significantly reduced within five of the eight assessed yoga classes, but there were no significant changes in cortisol levels. No significant correlations were found between VAS scores and salivary cortisol levels. When looking at how cortisol levels changed over time (i.e., over the series of eight yoga sessions), there was a significant downward trajectory in post-yoga cortisol, but not after taking pre-class cortisol into account (i.e., within yoga session cortisol change over time). Taken together, we found that subjective distress, but not cortisol was reduced by yoga classes. These data suggest that salivary cortisol did not match changes in perceived distress, thus emphasizing the ongoing challenges of relating subjective and objective measures.

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Perceived distress can negatively impact post-concussive symptoms.

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Efforts are needed to relate objective and subjective measures of distress.

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Subjective distress and salivary cortisol were examined within yoga sessions.

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Subjective distress, but not cortisol was reduced within 5 of 8 yoga classes.

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These data highlight the challenges of relating subjective and objective measures.

Identifying Trends of Dysautonomia Signs and Symptoms Associated with Protracted Concussion Recovery during the Buffalo Concussion Treadmill Test: A Retrospective Study

Objective:

To identify trends of provoked dysautonomia signs and symptoms during the Buffalo Concussion Treadmill Test (BCTT).

Subjects:

This is a retrospective cohort study of 101 patient charts post-concussion who were screened for suspected dysautonomia.

Methods:

Patients with suspected dysautonomia were assessed for exercise intolerance using a BCTT. Symptoms and rate of perceived exertion were recorded on a standardized form. Digital pulse oximetry was used to collect heart rate (HR) and oxygen saturation. Descriptive analyses were conducted on BCTT results.

Results:

Of 101 patient charts, 57 were excluded from analysis, including four patients who completed the BCTT by asymptomatically reaching the target HR zone for their estimated HR max. The remaining 44 patients demonstrated: 35 (79.5%) poor HR stabilization defined as a drop or plateau in HR during exercise, 28 (63.8%) exacerbated concussion symptoms, 13 (29.5%) autonomic nervous system response such as hot flushed sensation, 12 (27.3%) rebound symptoms during recovery phases, and 8 (18.2%) desaturation of 90% or below. The mean delta (80% expected HR max – 80% achieved HR max) on the initial test was 80.66 (± 23.08) beats per minute.

Conclusions:

This study is the first to identify trends of signs and symptoms during the BCTT in an expanded population with suspected dysautonomia after concussion. Future studies are indicated to validate these findings and contribute to development of modified termination criteria for the BCTT in individuals with suspected dysautonomia associated with protracted concussion recovery.

Identifying Trends of Dysautonomia Signs and Symptoms Associated with Protracted Concussion Recovery during the Buffalo Concussion Treadmill Test: A Retrospective Study

OBJECTIVE

To identify trends of provoked dysautonomia signs and symptoms during the Buffalo Concussion Treadmill Test (BCTT).

SUBJECTS

This is a retrospective cohort study of 101 patient charts post-concussion who were screened for suspected dysautonomia.

METHODS

Patients with suspected dysautonomia were assessed for exercise intolerance using a BCTT. Symptoms and rate of perceived exertion were recorded on a standardized form. Digital pulse oximetry was used to collect heart rate (HR) and oxygen saturation. Descriptive analyses were conducted on BCTT results.

RESULTS

Of 101 patient charts, 57 were excluded from analysis, including four patients who completed the BCTT by asymptomatically reaching the target HR zone for their estimated HR max. The remaining 44 patients demonstrated: 35 (79.5%) poor HR stabilization defined as a drop or plateau in HR during exercise, 28 (63.8%) exacerbated concussion symptoms, 13 (29.5%) autonomic nervous system response such as hot flushed sensation, 12 (27.3%) rebound symptoms during recovery phases, and 8 (18.2%) desaturation of 90% or below. The mean delta (80% expected HR max â€" 80% achieved HR max) on the initial test was 80.66 (± 23.08) beats per minute.

CONCLUSIONS

This study is the first to identify trends of signs and symptoms during the BCTT in an expanded population with suspected dysautonomia after concussion. Future studies are indicated to validate these findings and contribute to development of modified termination criteria for the BCTT in individuals with suspected dysautonomia associated with protracted concussion recovery.

Autonomic dysfunction in adults following mild traumatic brain injury: A systematic review

BACKGROUND

Increasing evidence suggests autonomic nervous system (ANS) dysfunction may occur following mild traumatic brain injury (mTBI). Measures of heart rate, heart rate variability, blood pressure and baroreceptor sensitivity can be used to evaluate ANS dysfunction following mTBI.

OBJECTIVE

Summarize the evidence for ANS dysfunction in adults following mTBI.

METHODS

A search of Embase, MEDLINE, Cochrane Central Register, PsycINFO, CINAHL and SPORTDiscus databases was conducted. Search topics included: mTBI and ANS. Identified abstracts were independently reviewed by 2 reviewers followed by full text screening. Risk of bias was assessed using a modified SIGN checklist. A structured synthesis was performed.

RESULTS

Thirty-nine studies (combined 1,467 participants diagnosed with mTBI) evaluating ANS function were included. ANS function was evaluated under various conditions including: rest, during exertion, cold pressor test, Valsalva maneuver, using face cooling and eyeball pressure paradigms. Short-term or ultra-short-term recordings were most common. The majority of studies (28/39) were rated as "unacceptable" for quality of evidence.

CONCLUSIONS

Altered parameters of ANS function have been reported in multiple conditions following mTBI, both acutely and in the post-acute/chronic stages of recovery. However, due to methodological limitations, conclusions regarding the severity and timing of ANS dysfunction following mTBI cannot be drawn.

Autonomic Nervous System Activity during Refractory Rise in Intracranial Pressure

Refractory intracranial hypertension (RIH) is a dramatic increase in intracranial pressure (ICP) that cannot be controlled by treatment. Recent reports suggest that the autonomic nervous system (ANS) activity may be altered during changes in ICP. Our study aimed to assess ANS activity during RIH and the causal relationship between rising in ICP and autonomic activity. We reviewed retrospectively 24 multicenter (Cambridge, Tromso, Berlin) patients in whom RIH developed as a pre-terminal event after acute brain injury (ABI). They were monitored with ICP, arterial blood pressure (ABP), and electrocardiography (ECG) using ICM+ software. Parameters reflecting autonomic activity were computed in time and frequency domain through the measurement of heart rate variability (HRV) and baroreflex sensitivity (BRS). Our results demonstrated that a rise in ICP was associated to a significant rise in HRV and BRS with a higher significance level in the high-frequency HRV (p < 0.001). This increase was followed by a significant decrease in HRV and BRS above the upper-breakpoint of ICP where ICP pulse-amplitude starts to decrease whereas the mean ICP continues to rise. Temporality measured with a Granger test suggests a causal relationship from ICP to ANS. The above results suggest that a rise in ICP interacts with ANS activity, mainly interfacing with the parasympathetic-system. The ANS seems to react to the rise in ICP with a response possibly focused on maintaining the cerebrovascular homeostasis. This happens until the critical threshold of ICP is reached above which the ANS variables collapse, probably because of low perfusion of the brain and the central autonomic network.